Aviptadil (VIP, vasoactive intestinal peptide) has been used in the United States and in European countries for more than 2 decades in controlled experiments involving humans and animals. Aviptadil for injection is approved in combination with phentolamine for treatment of erectile dysfunction in the United Kingdom, Denmark and New Zealand. Pharmacology and toxicology of the endogenous peptide Aviptadil have been described in a large number of peer-reviewed publications since its discovery in the early 1970's.
Endogenous Aviptadil, also called vasoactive intestinal peptide (VIP), is a peptide which consists of 28 amino acids and which has following amino acid sequence (from the N- to the C-terminus): His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-Met-Ala-Val-Lys-Lys-Tyr-Leu-Asn-Ser-Ile-Leu-Asn (SEQ ID NO: 1).
Conformational analysis of Aviptadil by two-dimensional NMR and circular dichroism spectroscopy has shown an initial disordered N-terminus sequence of eight amino acid residues with two beta-turns, followed by two helical segments at residues 7-15 and 19-27 connected by a region of undefined structure that confers mobility to the peptide molecule. Endogenous Aviptadil is synthesized from a precursor molecule which contains 170 amino acids and is processed to its biologically active form via a signal peptidase in the endoplasmic reticulum and finally cleaved by prohormone convertases and by carboxypeptidase-B like enzymes to Aviptadil.
Aviptadil was first isolated from the intestine. Several years later Aviptadil was identified in the central and peripheral nervous system, and has since been recognized as a widely distributed neuropeptide, acting as a neurotransmitter or neuromodulator in many organs and tissues, including heart, lung, thyroid gland, kidney, immune system, urinary tract and genital organs.
The widespread distribution of Aviptadil in mammals, including humans, is correlated with its involvement in a wide variety of physiological activities including smooth muscle relaxation which leads to systemic vasodilation, increased cardiac output, bronchodilation, and regulation of arterial pulmonary blood pressure, gastrointestinal smooth muscle cell relaxation and some differential effects on secretory processes in the gastrointestinal tract and gastric motility, hyperglycemia, inhibition of smooth muscle cell proliferation, hormonal regulation, analgesia, hyperthermia, neurotropic effects, learning and behavior, and bone metabolism.
Aviptadil is acid-labile and thermo-labile in isotonic salt solutions between 30° C. to 60° C.
Historically, Aviptadil was used over a long period of time in various human clinical trials administered either via the intravenous, intracavernous, or inhalative route. The current state of the art method for the preparation of a clinically applicable Aviptadil as a single medicament comprises the synthetic generation of the Aviptadil substance as a white powder, which is subsequently reconstituted in 0.9% sodium chloride solution (isotonic solution) at a concentration of 0.033 mg/mL. In another composition with phentolamine, Aviptadil is dissolved in a phosphate buffer (pH values between 2 and 4.5) containing ethylene diaminetetraacetate (EDTA) as stabilizer (EP0493485; U.S. Pat. No. 5,236,904; U.S. Pat. No. 5,447,912; WO9505188).
Many factors affect the stability of a pharmaceutical product, including the chemical reactivity of the active ingredient(s), the potential interaction between active and inactive ingredients, the manufacturing process, the dosage form, the container closure system, and the environmental conditions encountered during shipment, storage, handling and length of time between manufacture and usage. Pharmaceutical product stability is determined by the chemical stability as well as the physical stability of the formulation. Physical factors including heat and light may initiate or accelerate chemical reactions.
Optimal physical stability of a formulation is very important for at least three primary reasons. First, a pharmaceutical product must appear fresh, elegant and professional when it is administered to a patient. Any change in physical appearance such as color changes of haziness can cause a patient or consumer to have less confidence in the product. Second, because some products are dispensed in multiple dose containers, uniformity of dose content of the active ingredient over time must be assured. A cloudy solution or a broken emulsion can lead to a non-uniform dosage pattern. Third, the active ingredient must be available to the patient throughout the expected shelf life of the preparation. A breakdown of the product to inactive or otherwise undesired forms can lead to non-availability of the medicament to the patient.
Stability of a pharmaceutical product, then, may be defined as the capability of a particular formulation to remain within its physical, chemical, microbiological, therapeutic and toxicological specifications.
A stable solution retains its original clarity, color, and odor throughout its shelf life. Retention of clarity of a solution is a main concern in maintaining physical stability. Solutions should remain clear over a relatively wide temperature range, such as 4° C. to about 37° C. At the lower range an ingredient may precipitate due to a lower solubility at that temperature, while at higher temperatures homogeneity may be destroyed by extractables from the glass containers or rubber closures. Thus, solutions of active pharmaceutical ingredients must be able to handle cycling temperature conditions. Similarly, a formulation should retain its color throughout this temperature range, and its odor should be stably maintained.
Small peptides are typically unstable and are susceptible to degradation in aqueous solution. In this regard, once Aviptadil has less than 90% of its labeled potency, it is no longer considered to be suitable for administration to a patient.
Various types of sugars, surfactants, amino acids and fatty acids, used singly or in combination, have been used in efforts to stabilize protein and peptide products against degradation. Wang and Hanson, J. Parenteral Science and Technology Supplement, 1988, Technical Report No. 10 describe parenteral formulations of proteins and peptides. Examples of excipients such as buffers, preservatives, isotonic agents, and surfactants are described by Manning et al., 6 Pharmaceutical Research, 1989, by Wang and Kowak, 34 J. Parenteral Drug Association 452, 1980, and Avis et al., Pharmaceutical Dosage Forms: Parenteral Medications, Vol. 1, 1992.
It is understood that the development of a suitable pharmaceutical formulation for administration to a subject is complex. A need exists in the art for pharmaceutical formulations of Aviptadil designed to provide a single or multiple doses having substantial stability when refrigerated and at room temperature. Further, a need exists in the art for a liquid pharmaceutical formulation packaged with an appropriate container/closure system that also minimizes the physical and chemical degradation of such peptides.
It is an object of current invention to provide an effective, more stable, liquid Aviptadil formulation for the manufacture of a medicament suitable for inhalative or injectable medical administration for patients in need thereof. In another embodiment, it is an object of the current invention to provide a liquid Aviptadil formulation that allows long term storage of a medicament containing Aviptadil, thereby facilitating simplified storage and shipment conditions. In yet another embodiment it is an object of the current invention to provide a liquid pharmaceutical composition containing a pharmacologically active amount of Aviptadil and a pharmacologically active amount of the following peptides: Cyclo D-Asp-Pro-D-Val-Leu-D-Trp, or Ser-Pro-Lys-Met-Val-Gln-Gly-Ser-Gly-Cys-Phe-Gly-Arg-Lys-Met-Asp-Arg-Ile-Ser-Ser-Ser-Ser-Gly-Leu-Gly-Cys-Lys-Val-Leu-Arg-Arg-His (SEQ ID NO: 2).